feat: thumbnail generator plugin with configurable size/format

- ThumbnailGeneratorPort in domain (bytes + config → resized bytes)
- adapters-thumbnail: ImageThumbnailGenerator using image crate
- ThumbnailGeneratorPlugin reads width/height/format/profile from step config
- PostgresDerivativeRepository + 012_derivatives migration
- Seeded in extract_metadata pipeline as step 2 (300x300 webp)
- Standalone generate_derivative pipeline for on-demand use

crates/worker/src/factories/infra.rs

@@ -1,7 +1,7 @@
 use adapters_postgres::{
-    PostgresAssetMetadataRepository, PostgresAssetRepository, PostgresJobBatchRepository,
-    PostgresJobRepository, PostgresPipelineRepository, PostgresPluginRepository,
-    PostgresSidecarRepository,
+    PostgresAssetMetadataRepository, PostgresAssetRepository, PostgresDerivativeRepository,
+    PostgresJobBatchRepository, PostgresJobRepository, PostgresPipelineRepository,
+    PostgresPluginRepository, PostgresSidecarRepository,
 };
 use std::sync::Arc;
 
@@ -12,6 +12,7 @@ pub struct Repos {
     pub plugin: Arc<PostgresPluginRepository>,
     pub asset: Arc<PostgresAssetRepository>,
     pub metadata: Arc<PostgresAssetMetadataRepository>,
+    pub derivative: Arc<PostgresDerivativeRepository>,
     pub sidecar: Arc<PostgresSidecarRepository>,
 }
 
@@ -24,6 +25,7 @@ impl Repos {
             plugin: Arc::new(PostgresPluginRepository::new(pool.clone())),
             asset: Arc::new(PostgresAssetRepository::new(pool.clone())),
             metadata: Arc::new(PostgresAssetMetadataRepository::new(pool.clone())),
+            derivative: Arc::new(PostgresDerivativeRepository::new(pool.clone())),
             sidecar: Arc::new(PostgresSidecarRepository::new(pool)),
         }
     }

crates/worker/src/factories/plugins.rs

@@ -1,6 +1,8 @@
 use crate::plugin_registry::InMemoryPluginRegistry;
-use crate::plugins::{MetadataExtractorPlugin, NoOpPlugin, SidecarSyncPlugin};
-use domain::ports::{MetadataExtractorPort, SidecarWriterPort};
+use crate::plugins::{
+    MetadataExtractorPlugin, NoOpPlugin, SidecarSyncPlugin, ThumbnailGeneratorPlugin,
+};
+use domain::ports::{MetadataExtractorPort, SidecarWriterPort, ThumbnailGeneratorPort};
 use std::sync::Arc;
 
 use super::Repos;
@@ -10,16 +12,23 @@ pub fn build_plugin_registry(
     file_storage: Arc<dyn domain::ports::FileStoragePort>,
     sidecar_writer: Arc<dyn SidecarWriterPort>,
     extractor: Arc<dyn MetadataExtractorPort>,
+    thumbnail_gen: Arc<dyn ThumbnailGeneratorPort>,
 ) -> InMemoryPluginRegistry {
     let mut registry = InMemoryPluginRegistry::new();
 
     registry.register(Arc::new(NoOpPlugin));
     registry.register(Arc::new(MetadataExtractorPlugin::new(
         repos.asset.clone(),
-        file_storage,
+        file_storage.clone(),
         repos.metadata.clone(),
         extractor,
     )));
+    registry.register(Arc::new(ThumbnailGeneratorPlugin::new(
+        repos.asset.clone(),
+        file_storage,
+        repos.derivative.clone(),
+        thumbnail_gen,
+    )));
 
     let export_handler = Arc::new(application::sidecar::ExportSidecarHandler::new(
         repos.metadata.clone(),

crates/worker/src/main.rs

@@ -53,11 +53,14 @@ async fn main() -> anyhow::Result<()> {
 
     let extractor: Arc<dyn domain::ports::MetadataExtractorPort> =
         Arc::new(adapters_exif::NomExifExtractor);
+    let thumbnail_gen: Arc<dyn domain::ports::ThumbnailGeneratorPort> =
+        Arc::new(adapters_thumbnail::ImageThumbnailGenerator);
     let registry = Arc::new(build_plugin_registry(
         &repos,
         file_storage,
         sidecar_writer,
         extractor,
+        thumbnail_gen,
     ));
     let process_next = Arc::new(build_process_next_handler(
         &repos,

crates/worker/src/plugins/mod.rs

@@ -1,7 +1,9 @@
 pub mod metadata_extractor;
 pub mod no_op;
 pub mod sidecar_sync;
+pub mod thumbnail_generator;
 
 pub use metadata_extractor::MetadataExtractorPlugin;
 pub use no_op::NoOpPlugin;
 pub use sidecar_sync::SidecarSyncPlugin;
+pub use thumbnail_generator::ThumbnailGeneratorPlugin;

crates/worker/src/plugins/thumbnail_generator.rs

@@ -0,0 +1,138 @@
+use async_trait::async_trait;
+use domain::{
+    entities::{DerivativeAsset, DerivativeProfile},
+    errors::DomainError,
+    ports::{
+        AssetRepository, DerivativeRepository, FileStoragePort, PluginExecutor,
+        ThumbnailGeneratorPort,
+    },
+    value_objects::{MetadataValue, StructuredData, SystemId},
+};
+use std::sync::Arc;
+use tracing::info;
+
+pub struct ThumbnailGeneratorPlugin {
+    asset_repo: Arc<dyn AssetRepository>,
+    file_storage: Arc<dyn FileStoragePort>,
+    derivative_repo: Arc<dyn DerivativeRepository>,
+    thumbnail_gen: Arc<dyn ThumbnailGeneratorPort>,
+}
+
+impl ThumbnailGeneratorPlugin {
+    pub fn new(
+        asset_repo: Arc<dyn AssetRepository>,
+        file_storage: Arc<dyn FileStoragePort>,
+        derivative_repo: Arc<dyn DerivativeRepository>,
+        thumbnail_gen: Arc<dyn ThumbnailGeneratorPort>,
+    ) -> Self {
+        Self {
+            asset_repo,
+            file_storage,
+            derivative_repo,
+            thumbnail_gen,
+        }
+    }
+}
+
+fn parse_profile(s: &str) -> DerivativeProfile {
+    match s {
+        "ThumbnailLarge" => DerivativeProfile::ThumbnailLarge,
+        "WebOptimized" => DerivativeProfile::WebOptimized,
+        "VideoSd" => DerivativeProfile::VideoSd,
+        _ => DerivativeProfile::ThumbnailSquare,
+    }
+}
+
+fn format_extension(format: &str) -> &str {
+    match format {
+        "jpeg" | "jpg" => "jpg",
+        "png" => "png",
+        _ => "webp",
+    }
+}
+
+#[async_trait]
+impl PluginExecutor for ThumbnailGeneratorPlugin {
+    fn plugin_name(&self) -> &str {
+        "thumbnail_generator"
+    }
+
+    async fn execute(
+        &self,
+        asset_id: Option<SystemId>,
+        _payload: &StructuredData,
+        config: &StructuredData,
+    ) -> Result<StructuredData, DomainError> {
+        let asset_id = asset_id.ok_or_else(|| {
+            DomainError::Validation("thumbnail_generator requires asset_id".into())
+        })?;
+
+        let width = config
+            .get_string("width")
+            .and_then(|s| s.parse().ok())
+            .unwrap_or(300u32);
+        let height = config
+            .get_string("height")
+            .and_then(|s| s.parse().ok())
+            .unwrap_or(300u32);
+        let format = config.get_string("format").unwrap_or("webp");
+        let profile = config
+            .get_string("profile")
+            .map(parse_profile)
+            .unwrap_or(DerivativeProfile::ThumbnailSquare);
+
+        let asset = self
+            .asset_repo
+            .find_by_id(&asset_id)
+            .await?
+            .ok_or_else(|| DomainError::NotFound(format!("Asset {} not found", asset_id)))?;
+
+        if !asset.mime_type.starts_with("image/") {
+            return Ok(StructuredData::new());
+        }
+
+        let source_bytes = self
+            .file_storage
+            .read_file(&asset.source_reference.relative_path)
+            .await?;
+
+        let output = self
+            .thumbnail_gen
+            .generate(&source_bytes, width, height, format)?;
+
+        let ext = format_extension(format);
+        let storage_path = format!("derivatives/{asset_id}_{profile:?}.{ext}");
+
+        let byte_len = output.bytes.len() as u64;
+        self.file_storage
+            .store_file(&storage_path, output.bytes)
+            .await?;
+
+        let mut derivative = match self
+            .derivative_repo
+            .find_by_asset_and_profile(&asset_id, profile)
+            .await?
+        {
+            Some(d) => d,
+            None => DerivativeAsset::new_pending(asset_id, profile, &storage_path),
+        };
+
+        derivative.storage_path = storage_path.clone();
+        derivative.mark_ready(&output.mime_type, byte_len, (output.width, output.height));
+        self.derivative_repo.save(&derivative).await?;
+
+        let mut result = StructuredData::new();
+        result.insert("thumbnail_path", MetadataValue::String(storage_path));
+        result.insert(
+            "thumbnail_width",
+            MetadataValue::Integer(output.width as i64),
+        );
+        result.insert(
+            "thumbnail_height",
+            MetadataValue::Integer(output.height as i64),
+        );
+
+        info!(asset_id = %asset_id, w = output.width, h = output.height, "thumbnail generated");
+        Ok(result)
+    }
+}